Fluid-actuated cylinders are known which have an elongated piston rod located in a cylinder housing and supported for longitudinal movement. In certain of these cylinders, typically referred to as “double rod end cylinders”, the rod is supported such that the ends of the rod project outwardly from opposite ends of the housing. A piston assembly is attached to the rod along the length of the rod, and includes a ring-shaped piston which is fluidly sealed to the housing as the rod reciprocates, to define first and second fluidly-separated chamber portions at opposite ends of the housing. The controlled introduction/removal of fluid in the chamber portion(s) moves the piston rod in the desired direction in the housing.
Various techniques have been developed to attach the piston assembly to the rod. One known technique is to have a pair of piston rod portions, and to capture the ring-shaped piston between the ends of the rod portions as the rod pistons are connected together (such as by a threaded connection). Another known technique is to turn and grind a unitary (one piece) piston rod, and to thread the piston rod into a piston. In this technique, the rod can have an enlarged, radially-projecting annular shoulder which is received within a counterbore in the piston, to properly locate the piston on the piston rod.
A still further technique is to provide two piston halves, screw threads on a piston rod, and to locate a wire in the slots defined by the threads. The piston halves are then screwed onto the piston rod against one another, with the wire retaining the piston halves on the rod.
The above techniques are useful in many applications; however, they can require special, higher-cost material for the piston rod; have concentricity issues (between the piston and rod; as well as between two piston portions); require tight tolerances between the inter-engaging threads; and can require complicated machining and/or assembly, which make many of these techniques expensive to manufacture and repair.
It is further known to form a groove in the piston rod and to locate a split ring in the groove, and then to connect the split ring by some means (such as screws or bolts) to the piston. Some applications of this technique use radial or axial pressure to retain the split ring within the groove, such as by threaded locking nuts bearing against one side of the split ring (U.S. Pat. No. 3,426,657); a two-piece piston ring clamped around a split ring (U.S. Pat. No. 4,004,499); or slip-fit locking nuts or bearing bands outwardly surrounding the split ring (U.S. Pat. No. 3,457,842). U.S. Pat. No. 4,180,274, as a further example, uses multiple tongue and grooves formed in the split ring and piston rod, and then an additional snap ring to retain the snap ring on the piston. However, as can be appreciated, these applications also require additional components, multiple machining steps and/or close tolerances with the piston and the split ring. As such, it is believed that, regardless of the technique used, several complex components and/or machining steps are necessary in the known prior art to hold the piston on the piston rod.
It is therefor believed there is a demand for an improved technique for attaching a piston to a piston rod, and particularly an improved technique for retaining a piston to a piston rod which employs a split ring, where the technique is simple and straightforward, does not require additional components or difficult machining steps, and thereby reduces the manufacturing and repair expenses associated with the fluid cylinder.